Optimization of an Emerging NDE Modality Using Coplanar Capacitors for Inspection of Dielectric Materials

Research and Review Journal of Nondestructive Testing, vol. 4

Abstract

This work aims to further advance the understanding of capacitive imaging and its potential for nondestructive evaluation (NDE). This electromagnetic technique uses electric fields to interrogate the dielectric properties of materials under test; it can identify changes in geometry, cracks, inclusions, and other discontinuities in dielectric materials. As a non-contact, single-sided access technique, capacitive imaging provides new and unique ways of inspecting materials. The probes and the measurement electronics are conceptually simple, a capacitive imaging setup could be made portable and cost-effective in comparison to other nondestructive testing (NDT) techniques. The capacitive imaging’s main challenges are: (i) a low signal-to-noise ratio (SNR), due to susceptibility to electrical noise, and (ii) a spatial resolution that is tied to the penetration depth. The work included here relates to the optimization of the driving parameters and capacitive transducer setup to increase the SNR, in general, and to link the signal features to material discontinuities. It was found that the SNR and dynamic range are mainly independent of the driving frequency, but heavily dependent on the driving voltage. Additionally, placing a metallic backing under a test piece, or even using external metal pieces as driving electrodes, greatly increases penetration depth and enables inspection of thick test pieces.

Authors 2

1. Lennart Bertram Aachen

   RWTH Aachen University · National Research Council Canada

   Affiliation as printed

   National Research Council Canada , 1200 Montreal Rd , Ottawa , ON K1A 0R6 , Canada

   RWTH Aachen University , Templergraben 55 , 52062 Aachen , Germany

2. Catalin Mandache

   National Research Council Canada

   Affiliation as printed

   National Research Council Canada , 1200 Montreal Rd , Ottawa , ON K1A 0R6 , Canada